BRAF mutation testing to determine eligibility for treatment with vemurafenib was performed on archival skin lesions of a 54-year-old patient diagnosed with Erdheim–Chester disease (ECD) in 1999. Sanger sequencing of DNA extracted from a 2008 skin lesion identified two non-contiguous base substitutions in BRAF, which were shown by next-generation sequencing (NGS) to be located in the same allele. Due to its long-standing duration, molecular evolution of disease was possible; however, both Sanger and NGS of a 2000 skin lesion were unsuccessful due to the poor quality of DNA. Finally, droplet digital PCR using a probe specific for this novel mutation detected the complex BRAF mutation in both the 2000 and 2008 lesions, indicating this case to be ECD with a novel underlying BRAF p.Thr599_Val600delinsArgGlu mutation. Although well at present, molecular modelling of the mutant BRAF suggests suboptimal binding of vemurafenib and hence reduced therapeutic effectiveness.
- Haematology (incl blood transfusion)
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Contributors JMB analysed sequencing results, collated the data and wrote the manuscript. JJR performed the Sanger sequencing and NGS library preparation. MAT performed the Sanger sequencing and designed the ddPCR probe. RA analysed the NGS. EG performed and analysed the ddPCR. RLM and MA performed the protein modelling. SF performed and reviewed the histopathology. PC (clinically) managed the case and provided the case presentation. JP managed the case. All authors were involved in the design of aspects of the analysis of this case and reviewed and approved the final version of the manuscript.
Competing interests None declared.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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